U.S. patent application number 15/048780 was filed with the patent office on 2016-08-25 for vehicle driving assistance appatarus.
The applicant listed for this patent is USHIO DENKI KABUSHIKI KAISHA. Invention is credited to Hidekazu Hatanaka, Masashi Okamoto.
Application Number | 20160247393 15/048780 |
Document ID | / |
Family ID | 56690513 |
Filed Date | 2016-08-25 |
United States Patent
Application |
20160247393 |
Kind Code |
A1 |
Okamoto; Masashi ; et
al. |
August 25, 2016 |
VEHICLE DRIVING ASSISTANCE APPATARUS
Abstract
A vehicle driving assistance apparatus installed in a vehicle
displays a predetermined light pattern on a road surface around an
own vehicle. The vehicle driving assistance apparatus includes a
coherent light source that emits a light source beam, a road
surface projection optical system that scans the light source beam
and emits the projection beam, a road surface presence information
retention section and a control circuit. The control circuit stops
the projection beam toward the position where the road surface is
absent.
Inventors: |
Okamoto; Masashi; (Hyogo,
JP) ; Hatanaka; Hidekazu; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
USHIO DENKI KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
56690513 |
Appl. No.: |
15/048780 |
Filed: |
February 19, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60Q 1/50 20130101; B60Q
2400/50 20130101; B60W 2552/20 20200201; B60W 2050/146 20130101;
B60Q 2300/32 20130101; B60Q 2300/324 20130101; F21Y 2115/30
20160801; B60Q 2300/146 20130101; B60W 50/14 20130101 |
International
Class: |
G08G 1/005 20060101
G08G001/005; B60Q 1/00 20060101 B60Q001/00; B60Q 1/26 20060101
B60Q001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2015 |
JP |
2015-031537 |
Claims
1. A vehicle driving assistance apparatus installed in an own
vehicle and configured to display a predetermined light pattern on
a road surface around the own vehicle to enable a driver of the
vehicle, a driver of another vehicle, a pedestrian, and an
environmental condition detector to recognize the displayed light
pattern, the vehicle driving assistance apparatus comprising: a
coherent light source that emits a light source beam; a road
surface projection optical system configured to scan the light
source beam and output a projection beam, the projection beam being
the scanned light source beam having the predetermined light
pattern; a road surface presence information retention section
configured to retain an information, the information depending on a
distance from the own vehicle and indicating whether the road
surface is present in a region where the projection beam is to be
projected; and a control circuit configured to control the coherent
light source and the road surface projection optical system, the
control circuit being configured to stop the output of the
projection beam toward a position at which absence of the road
surface is indicated by information, in the region where the
projection beam is to be projected, the information being retained
by the road surface presence information retention section.
2. The vehicle driving assistance apparatus according to claim 1,
wherein the road surface presence information retention section
includes a road surface absence detector that is configured to
detect whether the road surface is present in the region where the
projection beam is to be projected, the road surface absence
detector is configured to generate a road surface absence data, the
road surface absence data being information that depends on the
distance from the own vehicle and indicates whether the road
surface is present in the region where the projection beam is to be
projected.
3. A vehicle driving assistance apparatus comprising: a road
surface projection optical system configured to output a projection
beam; a road surface presence information retention section
configured to retain an information that, depending on a distance
from a vehicle, indicates whether a road surface is present or
absent in a region where the projection beam is to be projected;
and a control circuit configured to control the road surface
projection optical system, the control circuit being configured to
stop the output of the projection beam where the information
indicates that the road surface is absent.
4. The vehicle driving assistance apparatus according to claim 3,
wherein the road surface presence information retention section
includes a road surface absence detector that is configured to
detect whether the road surface is present or absent and to
generate the information.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Japanese Priority
Patent Application JP 2015-031537 filed on Feb. 20, 2015, the
entire contents of which are incorporated herein by reference.
BACKGROUND
[0002] The present disclosure relates to a vehicle driving
assistance apparatus that scans light emitted from a coherent light
source such as a semiconductor laser, to draw a predetermined light
pattern on a road surface around an own vehicle, and enables a
driver of the own vehicle, drivers of other vehicles, pedestrians,
and an environmental condition detector to recognize the drawn
light pattern, thereby contributing to road safety.
[0003] As an existing technology that displays any light pattern on
a road surface around an own vehicle with use of a laser beam such
as a semiconductor laser and enables a driver of the own vehicle,
drivers of other vehicles, pedestrians, and an environmental
condition detector to recognize the displayed light pattern, for
example, a technology disclosed in Japanese Unexamined Patent
Application Publication No. H05-238307 is exemplified. The
technology disclosed in this document projects a visible spot
marker or a diagram such as a polygon through scanning with use of
a two-dimensional galvanometer, on a front position distanced by a
predetermined length from the vehicle on a road surface. This makes
it possible to enable pedestrians and drivers of other vehicles to
recognize presence of the own vehicle.
[0004] Further, in Japanese Unexamined Patent Application
Publication No. 2003-231450, disclosed is a technology in which an
image pickup apparatus acquires a light pattern formed on a road
surface by a laser beam that is emitted by the own vehicle and
other vehicles and a condition to be noted in traveling of the own
vehicle is determined based on information of the light pattern. In
this technology, a traveling track where the own vehicle is
supposed to travel is calculated based on a vehicle speed, a motion
state quantity, a steering angle, and steering force of the own
vehicle. Right and left boundaries between a zone where the vehicle
passes and a zone where the vehicle does not pass in a case where
the own vehicle is assumed to travel on the calculated traveling
track are calculated, and a scan actuator scans a laser beam to
draw a part of the boundaries necessary for safety depending on the
speed and other factors.
[0005] Further, in Japanese Unexamined Patent Application
Publication No. 2004-526612, disclosed is a technology of
displaying a light pattern on a road surface behind the own vehicle
with use of a method used in a field of illumination effect for a
spectacular show, and providing a following vehicle with
information when an accident occurs or the own vehicle is urgently
stopped.
SUMMARY
[0006] These technologies just mentioned above are based on the
assumption that the projection beam forming the light pattern
projected on the road surface is irregularly reflected by the road
surface and is diffused substantially uniformly in all directions
less depending on an entering direction of the light. In addition,
these technologies are based on the assumption that emitting the
projection beam downward from a position as high as possible of a
vehicle, for example, in a case of a passenger car, from a vicinity
of a top side of a front windshield before a driver's seat does not
cause the projection beam to directly enter eyes of a driver of
other vehicle and pedestrians.
[0007] These technologies, however, may cause an issue when the
vehicle travels a place where a downward gradient of the road
surface increases as the distance from the own vehicle increases.
The issue is described with reference to FIGS. 3A to 3D that are
schematic diagrams each illustrating a concept relating to the
technology of a vehicle driving assistance apparatus according to
an embodiment of the disclosure. When the projection beam (Fo) is
projected forward, for example, as illustrated in FIGS. 3A and 3B,
the projection beam (Fo) forming a light pattern projected on the
road surface does not strike against the road surface at a place
immediately before an own vehicle (Co) travels the top of an uphill
or immediately before the own vehicle (Co) starts to travel a
downhill. When the projection beam (Fo) is projected backward, for
example, as illustrated in FIGS. 3C and 3D, the projection beam
(Fo) forming the light pattern projected on the road surface does
not strike against the road surface at a place immediately after
the own vehicle (Co) travels the top of the uphill or immediately
after the own vehicle (Co) starts to travel the downhill. The
projection beam (Fo) that has not struck against the road surface
brushes against the road surface forward. The projection beam (Fo)
may become relatively parallel to the road surface or travel upward
in a region away from the own vehicle. The projection beam (Fo) may
directly enter eyes of a driver of an oncoming vehicle (Cf) in the
case of forward projection, or may directly enter eyes of a driver
of a following vehicle (Cb) in the case of backward projection. If
such a phenomenon actually occurs, the driver is strongly dazzled
by the projection beam (Fo), which may cause a traffic
accident.
[0008] It is desirable to provide a vehicle driving assistance
apparatus that inhibits a projection beam that forms a light
pattern projected on a road surface from dazzling drivers of other
vehicles without striking against the road surface when the own
vehicle travels a place where a downward gradient of the road
surface increases as the distance from the own vehicle
increases.
[0009] A vehicle driving assistance apparatus according to an
embodiment of the disclosure is installed in a vehicle and displays
a predetermined light pattern (Q) on a road surface around an own
vehicle to enable a driver of the own vehicle, drivers of other
vehicles, pedestrians, and an environmental condition detector to
recognize the displayed light pattern. The vehicle driving
assistance apparatus includes: a coherent light source (Ds); a road
surface projection optical system (Up) configured to scan a light
source beam (Fb) that is light emitted from the coherent light
source (Ds), to output a projection beam (Fo), and project the
light pattern (Q) on the road surface around the own vehicle; a
road surface presence information retention section (Uw) configured
to retain information, the information depending on a distance from
the own vehicle and indicating whether the road surface is present
in a region where the projection beam (Fo) is to be projected; and
a control circuit (Ec) configured to control the coherent light
source (Ds) and the road surface projection optical system (Up).
The control circuit (Ec) stops the output of the projection beam
toward a position at which absence of the road surface is indicated
by information, in the region where the projection beam (Fo) is to
be projected. The information is retained by the road surface
presence information retention section (Uw).
[0010] It is possible to provide the vehicle driving assistance
apparatus that inhibits the projection beam that forms the light
pattern projected on the road surface from dazzling the drivers of
the other vehicles without striking against the road surface when
the own vehicle travels a place where the downward gradient of the
road surface increases as the distance from the own vehicle
increases.
[0011] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
and are intended to provide further explanation of the technology
as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings are included to provide a further
understanding of the disclosure, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments and, together with the specification, serve to explain
the principles of the technology.
[0013] FIG. 1 is a block diagram illustrating a vehicle driving
assistance apparatus according to an embodiment of the disclosure
in a simplified manner.
[0014] FIG. 2 is a pattern diagram illustrating one mode of a part
of the vehicle driving assistance apparatus according to the
embodiment of the disclosure in a simplified manner.
[0015] FIGS. 3A to 3D are schematic diagrams each illustrating a
concept relating to the technology of the vehicle driving
assistance apparatus according to the embodiment of the
disclosure.
DETAILED DESCRIPTION
[0016] First, a configuration of a vehicle driving assistance
apparatus according to an embodiment of the disclosure is described
with reference to FIG. 1 that is a block diagram illustrating the
vehicle driving assistance apparatus in a simplified manner. As
illustrated in FIG. 1, the vehicle driving assistance apparatus
(Uf) includes a road surface projection optical system (Up), a road
surface presence information retention section (Uw), and a control
circuit (Ec). The vehicle driving assistance apparatus (Uf) further
includes a conversion optical system (Bc) and a coherent light
source (Ds). The conversion optical system (Bc) provides a light
source beam (Fb) to the road surface projection optical system
(Up), and the coherent light source (Ds) provides emitted light
(Fs) to the conversion optical system (Bc). The control circuit
(Ec) performs control of the coherent light source (Ds) and the
road surface projection optical system (Up). The emitted light (Fs)
from the coherent light source (Ds) is converted into the light
source beam (Fb) by the conversion optical system (Bc). The light
source beam (Fb) is then provided to the road surface projection
optical system (Up). The light source beam (Fb) may have a
thickness suitable for being projected to a long distance. Note
that the conversion optical system (Bc) may be provided as
necessary. Examples of the conversion optical system (Bc) may
include a collimator lens and a beam expander. Also, examples of
the coherent light source (Ds) may include a semiconductor laser
and a light source that converts a wavelength of light emitted from
a semiconductor laser with use of a non-linear optical phenomenon
such as high frequency generation and optical parametric
effect.
[0017] The road surface projection optical system (Up) may include
a two-dimensional deflector. The two-dimensional deflector may
include two optical deflection devices such as an acousto-optical
deflection device (AOD) and a galvanometer mirror that are so
disposed as to be orthogonal in a deflection direction to each
other. The two-dimensional deflector may independently drive the
two optical deflection devices to emit the received beam toward an
optional direction. In a case where the optical deflection device
is the galvanometer mirror, a deflection angle of each of the two
optical deflection devices may be defined based on a magnitude of a
drive current flowing through a coil. In a case where the optical
deflection device is the acousto-optical deflection device, the
deflection angle of each of the two optical deflection devices may
be defined based on a frequency of a high-frequency drive voltage
applied to an ultrasonic wave transducer. The light source beam
(Fb) that has entered the road surface projection optical system
(Up) may be deflected in directions of azimuth angles .theta. and w
into a projection beam (Fo) to be emitted to outside of the vehicle
driving assistance apparatus (Uf). The emitted projection beam (Fo)
may reach the road surface around the own vehicle to form a beam
spot (P). Dynamically changing the azimuth angles .theta. and
.omega. may continuously move the beam spot (P), which enables the
road surface projection optical system (Up) to project an optional
light pattern (Q) such as a straight line, a curved line, a circle,
a polygon, and a character, on the road surface around the own
vehicle.
[0018] For example, drawing a boundary of the traveling lane of the
own vehicle as the light pattern (Q) may make it possible to cause
drivers of other vehicles and pedestrians to give attention to the
own vehicle and to allow a driver of the own vehicle to confirm
adequacy of own steering. The traveling lane used herein refers to
a region formed by moving the projection of the body of the own
vehicle at a certain moment on the road surface along with the
traveling of the vehicle and synthesizing the projected regions in
a sum-set and cumulative manner. Alternatively, the traveling lane
refers to a region formed by adding an allowance in a width
direction necessary for safety to the region formed in the
above-described manner. Further, the light pattern (Q) may be
projected not only to attract human attention but also to allow an
environmental condition detector to function. The environmental
condition detector may include, for example, an image pickup device
to acquire the reflected scattered light of the light pattern (Q)
as an image, and identify whether a reflection scattering body is a
road surface, a preceding vehicle, or an obstacle, thereby
extracting information of safe state in front of the own
vehicle.
[0019] The azimuth angles .theta. and .omega. used herein are
defined below for convenience of the following description. When
directing the traveling direction of the vehicle in straight
traveling in a state where the vehicle driving assistance apparatus
(Uf) is installed in the vehicle, a depression angle that is an
angle of the deflected beam in a perpendicular plane, namely, an
angle formed by the light beam with the road surface is denoted by
.theta., and an angle of the light beam in a horizontal plane is
denoted by .psi., where an axis parallel to the flat road surface
is referred to as a z-axis. Further, both of the angles .theta. and
.omega. are referred to as the azimuth angles.
[0020] The control circuit (Ec) modulates electric power supplied
to the coherent light source (Ds) with use of a light source
modulation signal (Ss), controls the coherent light source (Ds) to
be turned on or off, and controls intensity of light in lighting.
Further, the control circuit (Ec) may transmit target values
.theta.p and .psi.p of the azimuth angles .theta. and .omega. to
the road surface projection optical system (Up) with use of a
target azimuth angle signal (Sp). A drive circuit included in the
road surface projection optical system (Up) may control the drive
current and the drive voltage of the optical deflection devices to
achieve the target azimuth angles .theta.p and .psi.p.
[0021] The road surface presence information retention section (Uw)
retains road absence data (Sw) that is information depending on the
distance from the own vehicle and indicating whether a road surface
is present in a region where the projection beam (Fo) is to be
projected. The control circuit (Ec) may receive the road surface
absence data (Sw) to determine whether the road surface is present
or absent in the region where the projection beam (Fo) is to be
projected. Note that a method enabling the road surface presence
information retention section (Uw) to acquire the road surface
absence data (Sw) is described later. The control circuit (Ec)
stops the output of the projection beam (Fo) toward the position at
which absence of the road surface is indicated by the information
in the region where the projection beam (Fo) is to be projected. At
this time, the control circuit (Ec) controls one or both of the
coherent light source (Ds) and the road surface projection optical
system (Up).
[0022] Here, the road surface absence data (Sw) is information that
depends on the distance from the own vehicle and indicates whether
the road surface is present in the region where the projection beam
(Fo) is to be projected. Thus, the road surface absence data (Sw)
may be of any type as long as the road surface absence data (Sw)
allows determination of a situation in which the projection beam
(Fo) strikes against the road surface in a region within Z meters
(where Z is a specific value such as 30) from the own vehicle but
the downward gradient of the road surface increases and the road
surface where the projection beam (Fo) is to be projected is absent
in a region more than Z meters away from the own vehicle, which
causes the projection beam (Fo) to be emitted to a far region. In
other words, it is sufficient to determine the above-described
situation with use of the road surface absence data (Sw). Thus,
most simply, it is sufficient for the road surface absence data
(Sw) to include, as numerical information, the distance Z from the
own vehicle that is the limit value satisfying the condition that
the road surface is present in a region where the projection beam
(Fo) is to be projected.
[0023] Incidentally, in a situation where the road surface is flat
over a long distance and the road surface is present up to the
farthermost position where the projection beam (Fo) may possibly
project the light pattern (Q) (in other words, the distance Z is
substantially infinite), a specific value in a system (hardware and
software) of the vehicle driving assistance apparatus (Uf), for
example, a maximum value in the above-described numerical
information or an improbable negative value is assigned to the
value Zi in order to retain information of the situation as a value
Zi of the distance Z. As a result, the value Zi may be handled as a
predetermined factor.
[0024] When a height of the road surface projection optical system
(Up) from the road surface is denoted by h, the azimuth angle
.theta. is related with the distance Z by the following expression
(Expression 1).
Z=h/tan .theta.
[0025] Therefore, when the azimuth angle .theta. corresponding to
the distance Z is denoted by .theta.z, it is sufficient for the
road surface absence data (Sw) to include one of the distance Z or
the angle .theta.z. One of the values may be derived from the value
of the other side with use of the expression 1 as necessary. At
that time, a specific value such as zero and an improbable negative
value may be assigned to the angle .theta.z corresponding to the
above-described value Zi. Note that, as is clear from the above
description, the value Z is an upper limit of the distance and the
value Oz is a lower limit of the azimuth angle to satisfy the
condition that the road surface is present in the region where the
projection beam (Fo) is to be projected.
[0026] To stop the output of the projection beam (Fo) projecting
the light pattern (Q), for example, as the simplest way, the
control circuit (Ec) may control the road surface projection
optical system (Up) and the coherent light source (Ds) with
indifference whether the road surface is present in the region
where the projection beam (Fo) is to be projected. Then, the
control circuit (Ec) may additionally perform control to turn off
the coherent light source (Ds) when the azimuth angle .theta. or
the target azimuth angle .theta.p is equal to or lower than the
lower limit .theta.z that is obtained from the road surface absence
data (Sw). Incidentally, in the case of such simple control, the
road surface projection optical system (Up) may uselessly operate
even during a period in which the coherent light source (Ds) is off
by the additional control. Thus, the control circuit (Ec) may so
perform control as to omit a part, of the control sequence, after
the azimuth angle .theta. or the target azimuth angle .theta.p
becomes equal to or lower than the lower limit until the azimuth
angle .theta. or the target azimuth angle .theta.p exceeds the
lower limit again, which makes it possible to avoid the useless
operation mentioned above.
[0027] Note that in comparison of the actual azimuth angle .theta.
or the target azimuth angle .theta.p with the lower limit .theta.z,
the lower limit .theta.z may be desirably evaluated on a safe side,
namely, evaluated slightly larger in order to avoid occurrence of a
phenomenon in which the projection beam (Fo) is emitted to a far
region without striking against the road surface. The phenomenon
may be derived from fluctuation of a depression angle of the
projection beam (Fo) with the road surface as a reference caused by
pitching in which floating/sinking occurs at different timings
between a front part and a rear part of the car body, and other
factors. Alternatively, consideration for safety is reinforced, and
the coherent light source (Ds) may be turned off irrespective of
the actual azimuth angle .theta. or the target azimuth angle
.theta.p during a period in which the lower limit .theta.z does not
correspond to the value Zi.
[0028] As mentioned above, the vehicle driving assistance apparatus
(Uf) according to the embodiment of the disclosure scans the
emitted light (Fs) from the coherent light source (Ds) such as a
semiconductor laser, draws the predetermined light pattern (Q) on
the road surface around the own vehicle, and enables a driver of
the own vehicle, drivers of other vehicles, pedestrians, and the
environmental condition detector to recognize the drawn light
pattern (Q). This contributes to road safety and inhibits the
projection beam that forms the light pattern projected on the road
surface from dazzling the drivers of the other vehicles without
striking against the road surface when the own vehicle travels a
place where the downward gradient of the road surface increases as
the distance from the own vehicle increases. This makes it possible
to prevent occurrence of a traffic accident caused by
dazzlement.
[0029] Various methods are available to realize the road surface
presence information retention section (Uw). For example, GPS
technology may be used to track the ever-changing position of the
own vehicle, and information relating variation of the gradient of
a front road surface or a rear road surface may be acquired from
installed map information or map information downloaded through a
radio wave, thereby generating the lower limit .theta.z of the
azimuth angle on the ever-changing front side or the ever-changing
rear side of the own vehicle to satisfy the above-described
condition that the road surface is present. At this time, mounting
a gravity sensor and an acceleration sensor on the vehicle may make
it possible to actually measure the ever-changing gradient of the
road surface where the own vehicle is traveling. It is possible to
enhance generation accuracy of the lower limit .theta.z by
employing the actual measured value. In particular, regarding the
rear side of the own vehicle, it is possible to generate a
substantially accurate lower limit .theta.z from history data of
the actual measured gradients of the road surface where the own
vehicle has traveled.
[0030] Alternatively, the road surface presence information
retention section (Uw) may be realized by a road surface absence
detector (Xw) that detects absence of the road surface in the
region away from the own vehicle by a certain distance. Some
specific but non-limiting examples of the configuration thereof are
described below. For example, when an image pickup device is
provided to acquire a road condition (i.e., scenery) in front of or
behind the own vehicle as an image and, for example, an image
analysis apparatus determines whether a road surface is viewed on a
horizontal line at a certain height in the image, this
configuration functions as the road surface absence detector (Xw).
Thus, it is possible to determine a limit depression angle at which
the road surface is present, namely, to measure the lower limit
.theta.z of the azimuth angle satisfying the condition that the
road surface is present, by examining an upper limit of the height
at which the road surface is viewable on the image, based on the
image analysis. As illumination for picking up an image of the road
condition, outside light originally existing therearound, namely,
sunlight and light from a street lamp may be used; however,
invisible illumination light such as infrared light may be
preferably applied only to a necessary solid angle region from the
own vehicle. At this time, an illumination light source having a
spectrum width as narrow as possible (for example, an infrared
semiconductor laser) may be used and an image is picked up through
an interference filter matching with the spectrum range disposed in
front of the illumination light source. This makes it possible to
perform measurement less affected by outside light.
[0031] Further, when the illumination light source is modulated to
repeat lighting and extinction and only information coincident with
the modulated frequency component is acquired, the measurement may
become further less affected by outside light. In particular, using
a technology of frame synchronization illumination image processing
may make it possible to generate the road surface absence data (Sw)
based on the measurement extremely less affected by outside light,
and realize the excellent road surface absence detector. In this
technology, the illumination light source is modulated in
synchronization with a frame generation period of the image pickup
device to alternately generate a frame with lighted illumination
light source and a frame without lighted illumination light source,
and then image data of the frame without lighted illumination light
source is subtracted from image data of the frame with lighted
illumination light source.
[0032] Alternatively, instead of the dedicated illumination light
source as just mentioned above, the road surface projection optical
system (Up) of the vehicle driving assistance apparatus (Uf) may
project a test light pattern on a specific region of the road
surface around the own vehicle. The reflected scattered light of
the test light pattern may be acquired as an image with use of, for
example, an image pickup device provided in the road surface
projection optical system (Up), and the road surface absence
detector based on the image analysis may be accordingly configured
in a manner similar to the above description. Also in this case,
the projection beam (Fo) from the road surface projection optical
system (Up) may have a narrow spectrum width and may be subjected
to modulation. This makes it possible to achieve processing using
the interference filter and the frame synchronization illumination
image processing mentioned above. In the case of this technology,
however, the projection beam (Fo) may be visible light. Thus, to
prevent the component eventually lower than the lower limit
.theta.z out of the test light pattern from dazzling drivers of
other vehicles, it is necessary to intermittently perform
short-time projection of the test light pattern.
[0033] Alternatively, as described later, the road surface absence
detector based on the image analysis with use of the image pickup
device just mentioned above may be applied to the control method in
which the light pattern (Q) is projected while the lower limit
.theta.z is updated.
[0034] Further, as described later, the road surface absence
detection may be performed by, without using the image pickup
device, detecting the component inversely returned to the road
surface projection optical system (Up) out of the rear scattered
light on the road surface of the projection beam (Fo).
[0035] There is a following simple method to achieve the road
surface presence information retention section (Uw), alternative to
the automatically-operating road surface presence information
retention section (Uw) that is achieved by acquiring the road
surface gradient information or including the dedicated road
surface absence detector (Xw). As with manual switching over
between a high beam and a low beam of a headlight based on the
determination of the driver, for example, the driver himself may
determine whether the condition that the road surface is present in
the region where the projection beam (Fo) is to be projected is
satisfied up to a long distance, up to an intermediate distance, or
up to a close distance, and manually operate the switch to switch
over the above-described lower limit Oz of the azimuth angle in a
step-wise manner, thereby achieving the road surface absence
information retention section (Uw).
[0036] One fundamental note is supplementarily given here. A
question may arise that it would be better not to stop the output
of the projection beam in order to secure safety even though the
projection beam disadvantageously causes a side effect of
dazzlement to a driver of an oncoming vehicle when the own vehicle
travels a place where the downward gradient of the road surface
increases as the distance from the own vehicle increases. The
projection beam under the condition that the projection beam does
not strike against the road surface, however, does not form, on the
road surface, a light pattern effectively recognizable by a human
and the environment condition detector. Therefore, if such a
projection beam is outputted, no safety is provided to the own
vehicle. Such a projection beam may escape upward simply,
wastefully strike against the other vehicles, or dazzle the driver
of the oncoming vehicle as a side effect to enhance accident risk
of the oncoming vehicle. Accordingly, it is necessary to stop the
output of the projection beam under the above-described condition
as the best way. Safety to be given by the projection of the light
pattern is not given under such a condition. Therefore, to
compensate the lowered safety, it is necessary to take any other
effective measures beside the measure described in the embodiment
of the disclosure.
[0037] The embodiment of the disclosure is described below. First,
an optical system including the coherent light source (Ds) and the
road surface projection optical system (Up) that is configured
using a galvanometer mirror is described with reference to FIG. 2.
FIG. 2 is a pattern diagram illustrating one mode of a part of the
vehicle driving assistance apparatus according to the embodiment of
the disclosure. The emitted light from the coherent light source
(Ds) that is configured of the semiconductor laser may be
converted, through the conversion optical system (Bc), into the
light source beam (Fb) including optical fluxes parallel to one
another. The conversion optical system (Bc) may be a collimator
using an aspherical lens. The light source beam (Fb) may enter a
rotation mirror (Gr1) of a .theta.-deflection galvanometer mirror
(G1) through a polarization beam splitter (Bs) that is described
later. The rotation mirror (Gr1) may be fixed to an actuator shaft
(Gz) that reciprocatively rotates in response to the drive of an
actuator (Ga). The azimuth angle .theta. after deflection may be
controlled by a drive current that is allowed to flow through the
actuator (Ga) by the drive circuit (not illustrated) under the
control of the control circuit (Ec).
[0038] The beam that has been reflected by the rotation mirror
(Gr1) may enter a .psi.-deflection galvanometer mirror (G2), and
the azimuth angle .omega. after deflection may be controlled in a
similar manner. The .psi.-deflection galvanometer mirror (G2) has a
configuration similar to that of the .theta.-deflection
galvanometer mirror (G1) and has an actuator shaft orthogonal to
the actuator shaft (Gz). The beam that has been reflected by a
rotation mirror (Gr2) of the v-deflection galvanometer mirror (G2)
may be outputted as the projection beam (Fo) from the road surface
projection optical system (Up). The projection beam (Fo) may be
two-dimensionally deflected in an optional direction in a solid
angle region (A) and make it possible to project the light pattern
(Q) on the road surface around the own vehicle. Note that as a
position where the optical system in the drawing is to be disposed
in a vehicle, two points, a right end and a left end of an upper
side of a front windshield before a driver's seat from which the
road surface in front of the vehicle can be seen are suitable.
Alternatively, the optical system may be provided at only one
position of a center of the upper side of the front windshield,
namely, a gap between the front windshield and a room mirror.
[0039] In the case of the galvanometer mirror, a magnetic movable
part including the mirror has moment of inertia to rotation. For
example, when the drive current is varied in a stepwise manner in
order to hop and move the azimuth angle coordinates .theta. and
.psi., the current value does not correspond to the azimuth angles
.theta. and .psi. instantaneously because of the moment of inertia.
The azimuth angles .theta. and .psi. may rise at a finite speed and
approximate to a steady-state value while performing ringing
(attenuating oscillation). Accordingly, the azimuth angles .theta.
and .psi. may be detected and proportional-integral-derivative
(PID) feedback control may be performed to improve a response
speed, and the coherent light source (Ds) is turned off with use of
the light source modulation signal (Ss) to allow unnecessary track
of the beam spot (P) to be invisible during a period in which the
ringing or overshooting occurs. As described above, when the
driving is so performed as not to hop and move the azimuth angle
coordinates .theta. and .psi., but to gradually vary the azimuth
angles .theta. and .psi. in order to project a straight line or a
curved line, the ringing is difficult to occur. In such a case,
however, error caused by operation delay may occur between the
target azimuth angles .theta.p and .psi.p and the azimuth angles
.theta. and .omega., and as a result, error of the position and the
shape of the light pattern (Q) may occur. Therefore, correction is
necessary.
[0040] Some examples to configure the road surface absence detector
(Xw) generating information that depends on the distance from the
own vehicle and indicates whether the road surface is present or
absent in the region where the projection beam (Fo) is to be
projected have been described above. In FIG. 2, illustration
includes a configuration to achieve the road surface absence
detector through detection of a component that is inversely
returned to the road surface projection optical system (Up) out of
the rear scattered light on the road surface of the projection beam
(Fo). Assuming the case where the road surface is wet in the rainy
weather, preferably, the vehicle driving assistance apparatus (Uf)
may be so configured as to allow the projection beam (Fo) to become
the P-polarized wave to the water surface in order to suppress
regular reflection of light by the water on the road surface. Thus,
in the drawing, when the coherent light source (Ds) is so disposed
as to allow the polarized wave of the projection beam (Fo) to be
parallel to the .theta. direction and the polarization beam
splitter (Bs) is so disposed as to match thereto, about 100% of the
light source beam (Fb) may be ideally reflected toward the rotation
mirror (Gr1). When the projection beam (Fo) strikes against the
road surface to cause the rear scattered light, the polarization
plane may be typically rotated. Therefore, when the scattered light
returns from the road surface through the rotation mirror (Gr2) and
the rotation mirror (Gr1), the component that is S-polarized wave
with respect to the road surface may pass through the polarization
beam splitter (Bs), which may be detected by the light sensor
(Bx).
[0041] For example, the light sensor (not illustrated) may detect
the weak light of the light source beam (Fb) that has passed
through the polarization beam splitter (Bs), which may makes it
possible to constantly monitor the intensity of the light source
beam. A threshold of the ratio of the amount detected by the light
sensor (Bx) to the intensity of the light source beam is determined
through, for example, an experiment in order to recognize whether
the projection beam (Fo) strikes against the road surface. This
makes it possible to allow the configuration to function as the
road surface absence detector (Xw), and accordingly to achieve the
road surface presence information retention section (Uw) that
generates the road surface absence data (Sw). Note that the
detection efficiency of the return light by the light sensor (Bx)
depends on the distance Z that is a distance between the own
vehicle and a position where the projection beam (Fo) strikes
against the road surface. Therefore, the detection efficiency also
depends on the azimuth angle .theta. joined with the distance Z by
the above-described expression 1, and the above-described threshold
may be desirably determined dependently on the azimuth angle
.theta..
[0042] Note that a narrow band filter (Bf) using, for example, an
interference filter may be preferably disposed in front of the
light sensor (Bx) in order to avoid influence of sunlight, road
illumination light such as light from a street lamp, and
disturbance light such as light emitted from other vehicles.
Further, to enhance capability to avoid the influence of the
disturbance light, amplitude modulation of an appropriate frequency
may be performed on the drive current of the coherent light source
(Ds), and the road surface absence data (Sw) may be generated based
on a signal that has passed through an electric narrow band filter
corresponding to the frequency subjected to the amplitude
modulation, out of the signal detected by the light sensor (Bx).
Alternatively, technologies of synchronous detection and a lock-in
amplification circuit may be further used to generate the road
surface absence data (Sw) with higher detection accuracy. Also,
phase delay of the detection signal with respect to the modulation
signal is measured when the detection signal is accurately
acquired, which makes it possible to estimate the distance between
the own vehicle and the position where the projection beam (Fo)
strikes against the road surface.
[0043] As with the above description, the projection beam (Fo) may
be visible light. Thus, to avoid dazzlement to the drivers of the
other vehicles caused by the component eventually lower than the
lower limit .theta.z out of the light patterns (Q), a control
system that projects the light pattern (Q) while updating the lower
limit .theta.z as described below may be preferable. Specifically,
when the detection result of the road surface absence detector (Xw)
is monitored while projecting the light pattern (Q) and it is
determined that the projection beam (Fo) does not strike against
the road surface, the value of the lower limit .theta.z may be
immediately updated, and the projection of the light pattern in a
region in which the azimuth angle .theta. is lower than the lower
limit .theta.z is stopped. Then, to explore the possibilities that
the lower limit .theta.z is updated to a value lower than the
current value, the short-time projection of the light pattern (Q)
toward the region in which the azimuth angle .theta. is lower than
the current lower limit .theta.z may be intermittently performed to
monitor the detection result of the road surface absence detector
(Xw). When it is determined that the projection beam (Fo) strikes
against the road surface, the lower limit .theta.z may be updated,
and this operation may be repeated toward the direction where the
azimuth angle .theta. is gradually decreased.
[0044] Needless to say, the method using the road surface absence
detector (Xw) based on the detection of the return light by the
light sensor (Bx) just mentioned above may be applied to the method
of projecting the test light pattern on the specific position on
the road surface around the own vehicle by the road surface
projection optical system (Up).
[0045] A vehicle driving assistance system installed in the vehicle
may determine the shape of the traveling lane through simulation of
the ever-changing position and the ever-changing direction of the
own vehicle on the road surface until the near future. The vehicle
driving assistance system may perform the simulation with use of a
current steering angle by the driver, a change rate of the steering
angle by steering, a current speed of the vehicle, an acceleration
rate by operation of an accelerator, and an analysis of the road
condition in front of the vehicle acquired with use of an image
pickup device. The vehicle driving assistance system may determine
the shape of the light pattern to be projected to enable the driver
of the own vehicle, drivers of other vehicles, pedestrians, and the
environmental condition detector to recognize the light pattern.
Here, there may be a case where the light pattern to be projected
is a boundary of the traveling lane itself. The length of the light
pattern to be projected may depend on the speed of the own vehicle,
and a priority area of the light pattern to be projected may become
farther from the own vehicle as the speed of the own vehicle is
high.
[0046] The vehicle driving assistance system may convert
information indicating the shape of the light pattern to be
projected, from the plane coordinates on the road surface into the
azimuth angle coordinates .theta. and .omega.. The vehicle driving
assistance system may transmit, to the control circuit (Ec) of the
vehicle driving assistance apparatus (Uf) according to the
embodiment of the disclosure, data of the converted information,
for example, as a sequence of the target azimuth angles .theta.p
and .psi.p. The control circuit (Ec) may repeatedly read out the
received sequence of the target azimuth angles .theta.p and .psi.p,
and generate the light source modulation signal (Ss) and the target
azimuth angle signal (Sp) to control the coherent light source (Ds)
and the road surface projection optical system (Up).
[0047] Incidentally, the control circuit (Ec) stops the output of
the projection beam (Fo) toward the position at which absence of
the road surface is indicated by information that is retained by
the road surface presence information retention section (Uw), in
the region where the projection beam (Fo) is to be projected. In
other words, during a period in which the road surface projection
optical system (Up) indicates a part of the sequence of the angles
.theta.p and .psi.p having the target angle .theta.p lower than the
lower limit .theta.z obtained from the road surface absence data
(Sw), the control circuit (Ec) controls the light source modulation
signal (Ss) to turn off the coherent light source (Ds), thereby
stopping the output of the projection beam (Fo) projecting the
light pattern (Q).
[0048] It should be understood by those skilled in the art that
various modifications, combinations, sub-combinations, and
alterations may occur depending on design requirements and other
factors insofar as they are within the scope of the appended claims
or the equivalents thereof.
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